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Bad vibes in your industrial fan: quick fix or a symptom that something else is wrong? The causes run the spectrum, and it’s important to know what to look for when things start to shake and shimmy.

AirPro Sales Manager / Senior Application Engineer Chet White walks you through seven common causes of fan vibration issues and a few ways to remediate them in this whiteboard video.

Full Transcript:

If your fan is experiencing vibration problems, I’m sorry. It’s not very fun to go through vibration issues. Fans do ship from the shop having been balanced, but sometimes in the field, you can encounter vibration. These are some common reasons why there’s vibration in the field. We’ll talk about some ways that maybe you can mitigate them.

#1 Material Build-Up On the Wheel. We see this one quite commonly. If you’ve misfit an application with a fan that has the capacity to build up with material, when material loads up on that wheel, you can start to get vibration problems. When that happens, really your only solution sticking with the same fan is stopping it, waiting for everything to stop moving, locking it out, getting in and cleaning out the wheel, and starting it back up. Now you might want to look into replacing a fan of that type of wheel with something that can expel the material building up on it.

#2 The Fan Wheel Has Deteriorated. Depending on the reason for this, could be a fan that’s just 40 years old and it’s worn out, or it could be two years old, but it has a corrosive gas coming through that’s wearing out the wheel and causing the properties of the wheel to change. Due to the properties changing inside the fan housing on the wheel, you’ll start to experience vibration. And again, with that, oftentimes, you can just replace the wheel with a new one, maybe look at a different material if it’s showing corrosion.

#3 You may have loose fasteners. This one is actually quite common. It doesn’t take too long to fix. Just get out a drill, and fasten down all those fasteners, and sometimes you’ll see the vibration go away. This is especially noticeable in the vertical region if your vibration is on the vertical side of your bearing. A lot of times it can be due to the fasteners at the base of the fan not being secure enough to the floor.

#4 It could be a misalignment in your drive component. Now this one could be tricky, especially if you don’t have a laser to align things, but if you have a straight edge and you have a way to align, it’s possible that during a changeout sometime along the way, maybe you were replacing some parts in your fan, you put them back together, and you didn’t have alignment. Misalignment produces vibration. So to fix that, it needs to be aligned. Take your straight edge to it, figure out how to align your bearings, and your shaft, get your shaft into a coupling, your coupling to the motor, and make sure your drive is aligned.

#5 It’s possible that your bearings are defective. So defective bearings, you can start to get metal on metal if there’s no grease in the bearings. If the grease is broken down and you’ve got bad grease in the bearings, you can start to see the bearings fail. When bearings fail, that’s usually detected through vibration - the fan’s no longer running smoothly. If your bearings are defective, they need to be replaced - both of them.

#6 Your fan could be operating near its system critical speed, or it could be in the stalling or unstable region of the curve. So when I’m talking about the stalling unstable region of the curve, we’re really referring to a curve like this, the region that’s right here. That’s the unstable region, and you could be having surge due to that region, and it really manifests itself in vibration. So if you’re getting vibration due to that issue, that could be a more serious issue that requires a look at the entire fan in the system while you’re operating there. That could be a little more challenging to fix… or it could be as easy as closing a damper. It’s possible a damper is closed too much, and you’ve pushed yourself too far to the left, but that also will reveal itself in vibrations.

The final common thing we see that produces vibrations is that it’s operating in - or near - a resonant frequency. Yeah. Your resonant frequencies are going to be anywhere in that 0-60 hertz fan, it could be greater than 60 hertz where you’re just operating in a specific frequency that’s not good for the wheel design of the fan, and so you need to make sure if you’re having vibrations due to that, that you avoid those frequencies that are exciting you fan and causing vibrations.

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